1. Technical Field
The present invention relates to a method of producing an electro-optical device for electrically connecting a first terminal portion provided on an electro-optical panel to a second terminal portion of a thin sheet substrate, and an electro-optical device.
2. Related Art
As is generally known, in an electro-optical device, for example, a light-transmissive liquid crystal device, a liquid crystal panel which is an electro-optical panel in which liquid crystal is disposed between two substrates made of glass, quartz, or the like is accommodated in a packaging case or the like.
In such a liquid crystal device, switching elements such as thin film transistors (hereinafter referred to as “TFTs”) and pixel electrodes are arranged on one of the substrates of the liquid crystal panel in a matrix pattern, and a counter electrode is arranged on the other substrate. An optical response of a liquid crystal layer disposed between the substrates is changed in accordance with image signals, thus enabling image display.
A TFT substrate on which TFTs are arranged and a counter substrate disposed so as to face the TFT substrate are separately produced. Each of the TFT substrate and the counter substrate is produced by laminating a semiconductor thin film, an insulating thin film, or a conducting thin film having a predetermined pattern on, for example, a quartz substrate. The semiconductor thin film, insulating thin film, or conducting thin film is formed by repeating a step of film deposition and a step of photolithography for each layer.
For example, when liquid crystal is provided between the TFT substrate and the counter substrate by a liquid crystal injecting method, the TFT substrate and the counter substrate thus produced are bonded with high accuracy (for example, within an alignment error of 1 μm) in a step of assembling a panel with a sealing material therebetween applied onto substantially the periphery of the substrates so as to have an opening in a part.
Subsequently, alignment is performed, and the substrates are pressure-bonded to cure the sealing material. Liquid crystal is then injected through the opening provided in the part of the sealing material. The opening is then sealed with a sealant cured by heating or the like.
For example, the TFT substrate is formed so as to be larger than the counter substrate in plan view. In this case, external connection terminals are arranged on a projecting portion disposed on a part of a surface of the TFT substrate, the surface having the counter substrate thereon, in a width direction connecting an edge of the liquid crystal panel to another edge thereof. Terminal portions of a flexible printed circuit (hereinafter referred to as “FPC”) which is a flexible, thin sheet substrate (not shown) having a specific length, the terminal portions being used for providing an electrical connection to external circuits of an electronic apparatus such as a projector, are electrically connected to the external connection terminals.
The terminal portions of the FPC are electrically connected to the external connection terminals by thermocompression bonding or the like via, for example, conductive particles such as metal particles in an anisotropic conductive adhesive such as an anisotropic conductive film (hereinafter referred to as “ACF”) or an anisotropic conductive paste (hereinafter referred to as “ACP”). Finally, the liquid crystal panel is accommodated in a packaging case or the like, thus producing a liquid crystal device.
For example, JP-A-2007-48801 discloses such a structure in which terminals are connected to each other via conductive particles in an anisotropic conductive adhesive. Specifically, JP-A-2007-48801 discloses a structure in which an electrical connection between terminals is reliably established by partially embedding metal particles, which function as conductive particles, mixed with an adhesive in a predetermined ratio in each of the terminals.
For example, a method of producing the above-mentioned TFT substrate is well known. Specifically, for example, a plurality of TFT substrates formed on a single large-plate quartz substrate are cut to a predetermined size, thereby producing the plurality of TFT substrates at the same time. When the size of the TFT substrates is decreased, the number of TFT substrates that can be produced at the same time using a single large-plate quartz substrate is increased, and thus the production cost can be reduced. This also applies to counter substrates.
However, when the size of the TFT substrates is decreased, the areas of external connection terminals are also decreased, that is, the connection areas of terminal portions of the FPC facing the external connection terminals are also decreased. Consequently, after connection, the terminal portions of the FPC are easily detached from the external connection terminals.
Accordingly, it has been desired to provide a method and structure in which an electrical connection between terminals can be reliably established, as compared with the method and structure disclosed in JP-A-2007-48801 in which terminals are electrically connected to each other by partially embedding conductive particles in each of the terminals.